void setup() {
  // set myFunction to be called everytime 
  // interrupt 2 is generated (everytime the pin gets from HIGH to LOW)    
  attachInterrupt(EXTERNAL_INTERRUPT_2, myFunction, FALLING); 
  
  // Starts serial to print data                                 
  Serial.begin(9600);                  
}

void loop() { 
 
}

void myFunction() {
  // WARNING: you should avoid doing long procedures in interrupt routines
  // Since this is an interrupt routine
  // and Serial is an interrupt driven output
  // interrupts must be enabled before printing
  interrupts();
  Serial.println("Interruption generated");
}